Report on COVID-19 Verification Case Study in Nine Countries Using the SIQR model

This report uses the SIQR model proposed by Takashi Odagaki to examine the epidemic trend of COVID-19 in nine major countries during February-May 2020, and to clarify the peculiar trend of infection in Japan. The SIQR model, which is an improvement on the conventional SIR model, is unique in that it allows us to theoretically clarify the epidemic phenomenon by separating the number of daily confirmed new cases by testing and the number of infecteds at large who remain untested, and also allows us to theoretically consider measures to control the epidemic. The infection control measures of each country were analyzed by dividing them into three groups according to the size of the decay (or growth) rate of infected at large ({lambda}). The active group includes China and South Korea, the passive group includes the United States and Sweden, and the average group includes Germany, Italy, France, Spain, and Japan. China and South Korea are the countries with the best testing and quarantine systems, and South Korea in particular having managed to contain the infection without lockdown through early quarantine by thorough testing. On the other hand, the United States and Sweden do not have a well-developed inspection and quarantine system and have shown little restraint in social distancing. In the case of Japan, the following special factors may have contributed to the extreme lack of PCR testing : (1) The "4-day fever rule" established by the Ministry of Health, Labour and Welfare was strictly enforced. (2) Even after the decision to postpone the Olympics, the government continued to monopolize PCR testing for the sake of unified analysis of infection data, and the policy of expanding PCR testing by private companies was not implemented.